HI TammyV,
Thank you so much for the love and care you show your little ones.
I do not have experience with liver shut surgery, but know it is an active topic here on YorkieTalk. Also have not had experience with tramadol.
If my little baby had been twitching/shaking for upwards of thirty minutes at a time, I'd be a royal mess--so my heart is breaking for you! Being told "it's probably normal" would not be a comfort to me at all.
Was the surgery performed by your gal's ordinary vet, or by a specialist? I'd be asking for more information from the vet and, if I still wasn't satisfied, would be making calls to a different vet for second opinion.
More than one thread on YorkieTalk concerning liver shunt encouraged pet owners to join what seems an active Yahoo Group dedicated to the subject.
Liver Shunt & MVD/HMD Support
If that link does not work, just search "Liver Shunt" from the Yahoo Groups front door. The group I'm referring to should be one of the first groups in the return list.